1. Field of the Invention
The present invention relates to reusable electrophotographic recording media in which image forming materials can be removed or erased away from electrophotographic recording media, on which images being recorded, thereby the electrophotographic recording media can be regenerated and reused for recording images; methods for producing the electrophotographic recording media; image forming methods that utilize the electrophotographic recording media; and methods for repeatedly using the electrophotographic recording media by repeating the forming and erasing of images.
2. Description of the Related Art
Recently, printers, analog copiers, and digital copiers on the base of electrophotographic system have widely spread and paper has been consumed concurrently in larger quantity. Paper utilized for the recording media is usually made from pulp derived from wood, thus volume consumption of paper leads to deforestation and deterioration of terrestrial environment. Accordingly, reducing the paper consumption is one of social subjects. In addition, waste disposals are restricted from the space and cost, thus reducing the waste products is also one of social subjects.
In order to address these problems, conventionally, used or spent information-recording paper is recovered, dissociated into pulp, and reused. However, such processes necessarily consume a large quantity of energy for recovering and transporting the paper, as well as for regenerating, making, and drying to produce new paper; and the resultant paper may be insufficient in the quality such that stiffness and whiteness are lower and bleeding tends to generate at subsequent printing processes. Further, the production of image recording paper with higher quality such as sufficient whiteness from the used or spent paper may possibly invite higher cost than from usual raw material, alternatively the production of image recording paper from the used or spent paper may possibly consume a larger amount of fossil fuel e.g. petroleum than the production of conventional new paper, in some cases.
In addition, recovering and regenerating the image-recorded recording media inevitably requires to collect the paper into plants or factories through transporting the image-recorded recording media from offices and homes, which possibly invites difficult issues in terms of maintaining confidentiality and privacy protection.
Accordingly, various recording media that enable to regenerate and reuse the recording media by erasing the recorded images thereon and methods to erase image-forming materials have been proposed in order to solve the problems with respect to recovering used paper and reusing as recycled paper. For example, Japanese Patent Application Laid-Open (JP-A) No. 01-297294 discloses a method for peeling away images by heating the images on recording media, formed from at least one of plastics, metals, liquid-impermeable papers, ceramics, etc., through interposing a heat-meltable peeling material.
JP-A No. 04-64472 discloses a method for erasing electrophotographic images formed on recording media, treated with a releasant, by way of transferring and peeling away the images by use of an endless belt on which a heat-meltable resin is provided.
JP-A No. 04-67043 discloses a recording medium, wherein one surface of sheet-like recording medium in particular is subjected to release-treatment and the surface-treated recording medium is marked to distinguish from plain paper.
The recording media illustrated above are generally not feasible on various grounds since the recording medium is based on plastics, or the toner repellent agent utilizes silicone sealants or commercial adhesive tapes.
Namely, in the recording media based on plastics, operators sometimes undergo electric shock from accumulated static electricity, since the recording media are charged when images on a photoconductor are transferred on the recording media under an electrophotographic process and the charged electricity hardly dissipates from the recording media even after the transfer is completed. Further, plastics are typically more expensive than paper. Moreover, recording media based on plastics cannot be easily reused unlike unnecessary paper, thus tend to put burden on environment.
On the other hand, toner repellent agents such as silicone compounds are disclosed in the prior art indicated above for making easy the image erasion. Further, JP-A No. 10-319620 discloses a reusable recording medium on which a silicone compound is applied, wherein a coated layer is applied in a coated amount of 2 g/m2 to 15 g/m2 on a recording surface of a support, the coated layer contains a filler and a resin, a releasant obtained from a composition that contains a modified silicone oil having a group reactive with silane compounds in the molecule is coated or impregnated on the coated layer and is dried, thereby the reusable recording medium is prepared.
It has been confirmed that application of silicone compounds on recording media may make possible to erase images on recording media by way of heating, pressuring-transferring, or rubbing without coating a releasant on the recording media.
However, the silicone compounds are relatively expensive, therefore the recording media are unfortunately expensive that utilize a silicone compound for the toner repellant. Further, the application of silicone compounds tends to lower excessively the fixing ability of images, which often causes such problems that image quality is poor due to offsets at image forming, alternatively image forming materials are fallen off when handling the recording media on which images being recorded, which makes the images illegible and/or the image forming materials smear the surroundings. In addition, writing implements such as water-based pens and oil-based pens are hardly allowable to write images on the recording media on which silicone compounds are coated.
Such toner repellency of silicone compounds cannot typically be reduced, for example, by being blended a resin with less or no toner repellency since the silicone compounds typically exhibit considerably low compatibility with other compounds, thus appropriate resins cannot be selected.
One of the specific reasons is that when a silicone compound and a resin other than silicone compounds are blended and coated to prepare recording media, the resultant recording media typically exhibit different effects on adhesion reduction of image forming materials, thus recording media with stable adhesive ability are hardly obtainable.
Further, silicone compounds typically have less or no aqueous solubility, thus it is difficult to coat using aqueous solvents. Currently, solvent-less silicone resins are commercially available that are curable by action of a catalyst. However, such resins typically involve difficulties in the production process that special coating apparatuses, e.g. gravure coaters, are necessary for coating and also pot life of the coating liquid is excessively short.
In order solve these problems, JP-A No. 06-219068 proposes a reusable recording medium, in which polyacrylates or polymethacrylates that contain a fluorinated alkyl group are employed as a toner repellent agent. However, fluorinated compounds are typically expensive, thus the recording medium is also expensive. In addition, since the toner repellency of fluorinated compounds is considerably intensive in general, the fixing ability between image forming materials and recording media can be hardly controlled. For example, when a fluorinated compound is employed that contains fluorine element within the molecule in a content to exhibit some toner repellency, the fixing ability of image forming materials may be excessively lowered, alternatively recording on image recording media is likely to be difficult by means of writing implements such as water-based pens and oil-based pens, thus the fixing ability of the image forming materials is hardly assured. Moreover, the fluorine compound disclosed in the literature are insoluble or less-soluble not only in water but also in conventional organic solvents, and a solvent containing halogen element are necessary for the coating process, thus environmental issues may be induced.
JP-A No. 08-286579 discloses a recording medium of which the contact angle with a liquid, having substantially the same surface tension with toners, is controlled into a certain range by use of a compound with an alkyl group such as alkylketene dimer on the surface of the recording medium. In the Examples of the literature, synthetic sizing agents of wax-like compounds such as alkylketene dimer are employed. It has been confirmed that the toner repellency of the surface of recording media can be controlled properly by using the alkylketene dimer and adjusting the content and/or mixing ratio with other materials.
However, alkylketene dimers for sizing agents are typically a single-molecular compound having a melting point of 40° C. to 70° C., thus tend to migrate into peeling members, image forming materials, and recording media, therefore, such problems are inevitable that the content or ratio of the alkylketene dimer at the surface region of the recording media tend to fluctuate and the reliability is insufficient under repeated usages.
Further, there exists a lack that small variation of conditions during the production tends to lead to the variation of the toner repellency. In the literature, sizing agents of styrene, olefin, and acrylic compounds are described to be usable in addition to the alkylketene dimers; however, no descriptions appear with respect to the specific constitutions or superior effects over the alkylketene dimers of the compounds.
JP-A No. 10-074025 discloses a recording medium that is added a toner repellent agent of a surfactant that comprises a fluorine-containing compound, silicone compound, and alkyl group-containing surfactant. However, the surfactant that comprises the fluorine-containing compound and/or silicone compound suffer from the same problems described above. Further, when the toner repellent agent of the surfactant that comprises the alkyl group-containing surfactant is utilized, there exist problems as described above that the content or ratio of the alkylketene dimer at the surface region of the recording media tend to migrate into peeling members, image forming materials, and recording media, similarly to the alkylketene dimer, and the reliability is insufficient under the repeated usages.